Nonmyeloablative conditioning generates autoantigen-encoding bone marrow that prevents and cures an experimental autoimmune disease.

Autoimmune diseases result from chronic targeted immune responses that lead to tissue pathology and disease. The potential of autologous hematopoietic stem cells transplantation as a treatment for autoimmunity is currently being trialled but disease relapse is an issue. We have previously shown in a mouse model of experimental autoimmune encephalomyelitis (EAE) that the transplantation of bone marrow (BM) transduced to encode the autoantigen myelin oligodendrocyte glycoprotein (MOG) can prevent disease induction. However these studies were performed using lethal irradiation to generate BM chimeras and a critical factor for translation to humans would be the ability to utilize low toxic preconditioning regimes. In this study, treosulfan was used as a nonmyeloablative agent to generate BM chimeras encoding MOG and assessed in models of EAE induction and reversal. We find that treosulfan conditioning can promote a low degree of chimerism that is sufficient to promote antigen specific tolerance and protect mice from EAE. When incorporated into a curative protocol for treating mice with established EAE, nonmyeloablative conditioning and low chimerism was equally efficient in maintaining disease resistance. These studies further underpin the potential and feasibility of utilizing a gene therapy approach to treat autoimmune disease.

Non-myeloablative transplantation of bone marrow expressing self-antigen establishes peripheral tolerance and completely prevents autoimmunity in mice.

Myeloablative transplantation of bone marrow (BM) engineered to express myelin oligodendrocyte glycoprotein (MOG) establishes central intrathymic tolerance and completely prevents MOG-induced experimental autoimmune encephalomyelitis (EAE) in mice. Here we asked whether non-myeloablative transplantation of MOG expressing BM (pMOG-bone marrow transplantation (BMT)) can also provide the same protection. Using stepwise reduction of irradiation doses, 275 cGy irradiation with pMOG-BMT protected 100% of mice from EAE development even with two subsequent re-challenge with MOG. Irradiation doses <275 cGy produced dose-dependent partial protection with significant disease protection still evident at 50 cGy. Splenocytes from 275 cGy recipients proliferated to MOG stimulation in vitro, indicating that MOG-reactive cells are present in the periphery but failed to induce disease. MOG-stimulated splenocytes produced little or no interleukin-17, interferon-γ, granulocyte-monocyte colony stimulating factor and tumor necrosis factor-α compared with EAE control. Adoptive transfer of CD4 T cells from EAE-resistant mice into Rag2(-/-) mice devoid of MOG expression resulted in MOG-induced EAE in ~74% of mice. Treatment of EAE-resistant mice with anti-programmed death 1 (PD-1) monoclonal antibody-induced EAE in 67% of mice. We conclude that non-myeloablative transplantation of self-antigen expressing BM induces robust peripheral tolerance that completely prevented EAE development. Our findings implicate clonal anergy and the PD-1 pathway in the maintenance of peripheral tolerance.

Local transgenic expression of granulocyte macrophage-colony stimulating factor initiates autoimmunity.

Mechanisms leading to breakdown of immunological tolerance and initiation of autoimmunity are poorly understood. Experimental autoimmune gastritis is a paradigm of organ-specific autoimmunity arising from a pathogenic autoimmune response to gastric H/K ATPase. The gastritis is accompanied by autoantibodies to the gastric H/K ATPase. The best characterized model of experimental autoimmune gastritis requires neonatal thymectomy. This procedure disrupts the immune repertoire, limiting its usefulness in understanding how autoimmunity arises in animals with intact immune systems. Here we tested whether local production of GM-CSF, a pro-inflammatory cytokine, is sufficient to break tolerance and initiate autoimmunity. We generated transgenic mice expressing GM-CSF in the stomach. These transgenic mice spontaneously developed gastritis with an incidence of about 80% after six backcrosses to gastritis-susceptible BALBc/CrSlc mice. The gastritis is accompanied by mucosal hypertrophy, enlargement of draining lymph nodes and autoantibodies to gastric H/K ATPase. An infiltrate of dendritic cells and macrophages preceded CD4 T cells into the gastric mucosa. T cells from draining lymph nodes specifically proliferated to the gastric H/K ATPase. CD4 but not CD8 T cells transferred gastritis to nude mouse recipients. CD4(+) CD25(+) T cells from the spleen retained anergic suppressive properties that were reversed by IL-2. We conclude that local expression of GM-CSF is sufficient to break tolerance and initiate autoimmunity mediated by CD4 T cells. This new mouse model should be useful for studies of organ-specific autoimmunity.